text: /*
   * inode.c
   *
   * Copyright (c) 1999 Al Smith
   *
   * Portions derived from work (c) 1995,1996 Christian Vogelgsang,
   *              and from work (c) 1998 Mike Shaver.
   */
  
  #include <linux/buffer_head.h>
  #include <linux/module.h>
  #include <linux/fs.h>
  #include "efs.h"
  #include <linux/efs_fs_sb.h>
  
  static int efs_readpage(struct file *file, struct page *page)
  {
  	return block_read_full_page(page,efs_get_block);
  }
  static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
  {
  	return generic_block_bmap(mapping,block,efs_get_block);
  }
  static const struct address_space_operations efs_aops = {
  	.readpage = efs_readpage,
  	.bmap = _efs_bmap
  };
  
  static inline void extent_copy(efs_extent *src, efs_extent *dst) {
  	/*
  	 * this is slightly evil. it doesn't just copy
  	 * efs_extent from src to dst, it also mangles
  	 * the bits so that dst ends up in cpu byte-order.
  	 */
  
  	dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
  	dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
  				((unsigned int) src->raw[2] <<  8) |
  				((unsigned int) src->raw[3] <<  0);
  	dst->cooked.ex_length =  (unsigned int) src->raw[4];
  	dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
  				((unsigned int) src->raw[6] <<  8) |
  				((unsigned int) src->raw[7] <<  0);
  	return;
  }
  
  struct inode *efs_iget(struct super_block *super, unsigned long ino)
  {
  	int i, inode_index;
  	dev_t device;
  	u32 rdev;
  	struct buffer_head *bh;
  	struct efs_sb_info    *sb = SUPER_INFO(super);
  	struct efs_inode_info *in;
  	efs_block_t block, offset;
  	struct efs_dinode *efs_inode;
  	struct inode *inode;
  
  	inode = iget_locked(super, ino);
  	if (!inode)
  		return ERR_PTR(-ENOMEM);
  	if (!(inode->i_state & I_NEW))
  		return inode;
  
  	in = INODE_INFO(inode);
  
  	/*
  	** EFS layout:
  	**
  	** |   cylinder group    |   cylinder group    |   cylinder group ..etc
  	** |inodes|data          |inodes|data          |inodes|data       ..etc
  	**
  	** work out the inode block index, (considering initially that the
  	** inodes are stored as consecutive blocks). then work out the block
  	** number of that inode given the above layout, and finally the
  	** offset of the inode within that block.
  	*/
  
  	inode_index = inode->i_ino /
  		(EFS_BLOCKSIZE / sizeof(struct efs_dinode));
  
  	block = sb->fs_start + sb->first_block + 
  		(sb->group_size * (inode_index / sb->inode_blocks)) +
  		(inode_index % sb->inode_blocks);
  
  	offset = (inode->i_ino %
  			(EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
  		sizeof(struct efs_dinode);
  
  	bh = sb_bread(inode->i_sb, block);
  	if (!bh) {
  		pr_warn("%s() failed at block %d\n", __func__, block);
  		goto read_inode_error;
  	}
  
  	efs_inode = (struct efs_dinode *) (bh->b_data + offset);
      
  	inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
  	set_nlink(inode, be16_to_cpu(efs_inode->di_nlink));
  	i_uid_write(inode, (uid_t)be16_to_cpu(efs_inode->di_uid));
  	i_gid_write(inode, (gid_t)be16_to_cpu(efs_inode->di_gid));
  	inode->i_size  = be32_to_cpu(efs_inode->di_size);
  	inode->i_atime.tv_sec = be32_to_cpu(efs_inode->di_atime);
  	inode->i_mtime.tv_sec = be32_to_cpu(efs_inode->di_mtime);
  	inode->i_ctime.tv_sec = be32_to_cpu(efs_inode->di_ctime);
  	inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
  
  	/* this is the number of blocks in the file */
  	if (inode->i_size == 0) {
  		inode->i_blocks = 0;
  	} else {
  		inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
  	}
  
  	rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
  	if (rdev == 0xffff) {
  		rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
  		if (sysv_major(rdev) > 0xfff)
  			device = 0;
  		else
  			device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
  	} else
  		device = old_decode_dev(rdev);
  
  	/* get the number of extents for this object */
  	in->numextents = be16_to_cpu(efs_inode->di_numextents);
  	in->lastextent = 0;
  
  	/* copy the extents contained within the inode to memory */
  	for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
  		extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
  		if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
  			pr_warn("extent %d has bad magic number in inode %lu\n",
  				i, inode->i_ino);
  			brelse(bh);
  			goto read_inode_error;
  		}
  	}
  
  	brelse(bh);
  	pr_debug("efs_iget(): inode %lu, extents %d, mode %o\n",
  		 inode->i_ino, in->numextents, inode->i_mode);
  	switch (inode->i_mode & S_IFMT) {
  		case S_IFDIR: 
  			inode->i_op = &efs_dir_inode_operations; 
  			inode->i_fop = &efs_dir_operations; 
  			break;
  		case S_IFREG:
  			inode->i_fop = &generic_ro_fops;
  			inode->i_data.a_ops = &efs_aops;
  			break;
  		case S_IFLNK:
  			inode->i_op = &page_symlink_inode_operations;
  			inode_nohighmem(inode);
  			inode->i_data.a_ops = &efs_symlink_aops;
  			break;
  		case S_IFCHR:
  		case S_IFBLK:
  		case S_IFIFO:
  			init_special_inode(inode, inode->i_mode, device);
  			break;
  		default:
  			pr_warn("unsupported inode mode %o\n", inode->i_mode);
  			goto read_inode_error;
  			break;
  	}
  
  	unlock_new_inode(inode);
  	return inode;
          
  read_inode_error:
  	pr_warn("failed to read inode %lu\n", inode->i_ino);
  	iget_failed(inode);
  	return ERR_PTR(-EIO);
  }
  
  static inline efs_block_t
  efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
  	efs_block_t start;
  	efs_block_t length;
  	efs_block_t offset;
  
  	/*
  	 * given an extent and a logical block within a file,
  	 * can this block be found within this extent ?
  	 */
  	start  = ptr->cooked.ex_bn;
  	length = ptr->cooked.ex_length;
  	offset = ptr->cooked.ex_offset;
  
  	if ((block >= offset) && (block < offset+length)) {
  		return(sb->fs_start + start + block - offset);
  	} else {
  		return 0;
  	}
  }
  
  efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
  	struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
  	struct efs_inode_info *in = INODE_INFO(inode);
  	struct buffer_head    *bh = NULL;
  
  	int cur, last, first = 1;
  	int ibase, ioffset, dirext, direxts, indext, indexts;
  	efs_block_t iblock, result = 0, lastblock = 0;
  	efs_extent ext, *exts;
  
  	last = in->lastextent;
  
  	if (in->numextents <= EFS_DIRECTEXTENTS) {
  		/* first check the last extent we returned */
  		if ((result = efs_extent_check(&in->extents[last], block, sb)))
  			return result;
      
  		/* if we only have one extent then nothing can be found */
  		if (in->numextents == 1) {
  			pr_err("%s() failed to map (1 extent)\n", __func__);
  			return 0;
  		}
  
  		direxts = in->numextents;
  
  		/*
  		 * check the stored extents in the inode
  		 * start with next extent and check forwards
  		 */
  		for(dirext = 1; dirext < direxts; dirext++) {
  			cur = (last + dirext) % in->numextents;
  			if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
  				in->lastextent = cur;
  				return result;
  			}
  		}
  
  		pr_err("%s() failed to map block %u (dir)\n", __func__, block);
  		return 0;
  	}
  
  	pr_debug("%s(): indirect search for logical block %u\n",
  		 __func__, block);
  	direxts = in->extents[0].cooked.ex_offset;
  	indexts = in->numextents;
  
  	for(indext = 0; indext < indexts; indext++) {
  		cur = (last + indext) % indexts;
  
  		/*
  		 * work out which direct extent contains `cur'.
  		 *
  		 * also compute ibase: i.e. the number of the first
  		 * indirect extent contained within direct extent `cur'.
  		 *
  		 */
  		ibase = 0;
  		for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
  			ibase += in->extents[dirext].cooked.ex_length *
  				(EFS_BLOCKSIZE / sizeof(efs_extent));
  		}
  
  		if (dirext == direxts) {
  			/* should never happen */
  			pr_err("couldn't find direct extent for indirect extent %d (block %u)\n",
  			       cur, block);
  			if (bh) brelse(bh);
  			return 0;
  		}
  		
  		/* work out block number and offset of this indirect extent */
  		iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
  			(cur - ibase) /
  			(EFS_BLOCKSIZE / sizeof(efs_extent));
  		ioffset = (cur - ibase) %
  			(EFS_BLOCKSIZE / sizeof(efs_extent));
  
  		if (first || lastblock != iblock) {
  			if (bh) brelse(bh);
  
  			bh = sb_bread(inode->i_sb, iblock);
  			if (!bh) {
  				pr_err("%s() failed at block %d\n",
  				       __func__, iblock);
  				return 0;
  			}
  			pr_debug("%s(): read indirect extent block %d\n",
  				 __func__, iblock);
  			first = 0;
  			lastblock = iblock;
  		}
  
  		exts = (efs_extent *) bh->b_data;
  
  		extent_copy(&(exts[ioffset]), &ext);
  
  		if (ext.cooked.ex_magic != 0) {
  			pr_err("extent %d has bad magic number in block %d\n",
  			       cur, iblock);
  			if (bh) brelse(bh);
  			return 0;
  		}
  
  		if ((result = efs_extent_check(&ext, block, sb))) {
  			if (bh) brelse(bh);
  			in->lastextent = cur;
  			return result;
  		}
  	}
  	if (bh) brelse(bh);
  	pr_err("%s() failed to map block %u (indir)\n", __func__, block);
  	return 0;
  }  
  
  MODULE_LICENSE("GPL");
  